07.03 pH

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Transcript of 07.03 pH

07.03 pHCalculations 1.) 34.0 mL - 50.0 mL =16.0 mL. 16 mL is the volume of sodium hydroxide. Conclusion 1.) NaOH is the base and HCI is the acid. As the amount of base increases, the reaction becomes less acidic. This explains the trend on the graph. It is considered neutral. The pH level is 7. The more NaOH that is added, the result shows that there are more drastic increases (because this means it is becoming more basic)

2.) It is important for someone to stir the solution in the flask because it increases the rate of the reaction. It also helps make sure that the reaction is finished before we make any conclusions.

3.)If a student did not remove all of the bubbles from inside the buret before reading the initial volume and beginning the titration would be higher than the actual concentration. The student would have overestimated the volume of the base because of the bubbles. When the student calculates molarity, it would also be higher then it actually is.

4.) 1. Adding too much base or acid. This would affect the volume by increasing the volume and decreasing the molarity. 2. The equipment being used is not pure. This could have a decrease a molarity, because there could be impurities in that solution. This could affect calculations and the titration itself. 3. A mathematical mistake. If someone records observations or follows the equation incorrectly could be strongly impacted on the calculations. Procedure(s)Data and Observations

Part I: Titration with an Indicator

1.) Fill the 50-milliliter buret with a 0.25 molar NaOH solution. 2.) Record volume. 3.)Measure out between 20 milliliters and 40 milliliters of the unknown HCl solution. 4.)Record volume. 5.)The amount of unknown HCl is then added to the 100-milliliter Erlenmeyer flask. 6.)Add two drops of the indicator, phenolphthalein, to the acid in the flask. 7.)Using the slider on the right hand side, add NaOH to the HCl in the Erlenmeyer flask (This action is known as titrate). Add the indicator until the color of the indicator turns a light shade of pink. 8.)Record the volume. 9.)If you went too far past the end point, please record the results of your trial. Include all sets of data in your lab report.

Part II: Titration with a pH Meter

1.) Fill the 50-milliliter buret with a 0.25 molar NaOH solution. 2.) Record volume. 3.) Measure out between 20 milliliters and 40 milliliters of the unknown HCl solution. This amount must be different than the amount used in part I. 4.) Record volume. 5.) The amount of unknown HCl is then added to the 100-milliliter Erlenmeyer flask. 6.) Insert the pH meter into the Erlenmeyer flask and record the initial pH of the acid. Remember to record the pH of the solution after every 5 milliliters of NaOH added. 7.) Titrate the NaOH into the HCl until the buret is empty.

Part 1Measurement What was MeasuredVolume of HCl usedInitial volume of NaOH in buretFinal volume of NaOH in buret20.0 mL50.0 mL34.0 mL Part 2

2.) 1 M * 16mL/38.08mL = 0.420 M.

ObservationThe color in the flask changed from colorless to a light pink that remained constant even after several seconds of stirring. Observation The pH meter detected a pH of 7.0 when 24.0 milliliters of sodium hydroxide had been added to the flask.